SCR Catalyst Diagnosis via Efficiency Thresholds
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Solution Overview
Problem
Current methods for diagnosing the efficiency of selective catalytic reduction (SCR) catalysts in internal combustion engines are either imprecise and lack repeatability or are intrusive, leading to false detections and overconsumption of urea with ammonia leaks.
Innovation Solution
A method that compares nitrogen oxide concentrations upstream and downstream of the SCR catalyst to determine treatment efficiency, using non-intrusive and passive calculations, and only performs an intrusive ammonia storage capacity diagnosis when efficiency thresholds are indeterminate, thereby ensuring reliable diagnosis and reducing urea emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-intrusive efficiency comparison method is used to diagnose SCR catalyst, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The diagnosis is segmented into two distinct phases: a non-intrusive efficiency comparison phase for routine monitoring, and an intrusive ammonia storage capacity phase for definitive diagnosis. This segmentation allows the system to maintain ease of operation during normal use while achieving measurement precision when needed.
Solution Approach 2:
The non-intrusive efficiency comparison is performed as a preliminary action before the intrusive ammonia storage capacity determination. This preliminary assessment filters out clearly healthy or clearly faulty catalysts, reserving the intrusive method only for indeterminate cases where high precision is actually needed.
2Measurement precision
If intrusive ammonia storage capacity determination is performed, then measurement precision is improved, but loss of substance worsens
Solution Approach 1:
The intrusive ammonia storage capacity determination is applied partially - only to the subset of cases where the non-intrusive efficiency comparison yields indeterminate results. This partial application minimizes the loss of urea and ammonia while maintaining measurement precision for the cases that require it.
Solution Approach 2:
The non-intrusive efficiency comparison serves as a preliminary filtering step that eliminates clearly healthy or faulty catalysts before the intrusive method is applied. This ensures the intrusive determination is performed only when necessary, reducing overall substance loss.
3Loss of substance
If non-intrusive efficiency comparison is used, then loss of substance is reduced, but reliability worsens
Solution Approach 1:
The diagnostic system is segmented into two methods with complementary roles: the non-intrusive efficiency comparison for initial screening (reducing substance loss) and the intrusive ammonia storage capacity determination for definitive diagnosis (ensuring reliability). Together, they achieve both goals.
Solution Approach 2:
The non-intrusive efficiency comparison acts as an intermediary step between the intrusive method and the final diagnosis. It filters cases before they reach the intrusive method, reducing substance loss while the intrusive method serves as the ultimate reliability check for indeterminate cases.
4Measurement precision
If intrusive method with operating parameter modification is applied, then measurement precision is improved, but productivity worsens
Solution Approach 1:
The intrusive method with operating parameter modification is applied partially - only to indeterminate cases identified by the preliminary efficiency comparison. This partial application maintains measurement precision for critical cases while preserving overall diagnostic productivity by avoiding unnecessary intrusive procedures.
Solution Approach 2:
The non-intrusive efficiency comparison is performed as a preliminary action to filter out cases that do not require the time-consuming intrusive method. This preliminary filtering significantly improves productivity by reducing the number of intrusive determinations needed while maintaining measurement precision for cases that require it.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides reliable and precise diagnosis of SCR catalysts without modifying operating parameters, reducing ammonia emissions and urea consumption.
Implementation Method 1
such an SCR catalyst makes it possible to reduce the molecules of nitrogen oxides (NOx) emitted in the combustion gases of the engine into molecules that are harmless to the environment, under the action of reducing agents injected continuously into the engine inlet of the SCR catalyst
Implementation Method 2
These performances, which can be defined as the efficiency of the nitrogen oxide reduction reaction in the SCR catalyst, are linked to the capacity of the latter to store ammonia NH3
Data Source
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AI summary
The invention relates to a method for diagnosing a SCR catalyst, comprising at least the steps of: determining (120) the effectiveness (ε) of the catalyst; comparing (130) said effectiveness (ε) with a first threshold (ε1); and deeming (140) the catalyst to be faulty when the effectiveness (ε) is lower than the first threshold (ε1), said method being characterised in that it includes at least the following steps: comparing (150) the effectiveness (ε) with a second threshold (ε2) which is higher than the first threshold (ε1); when the effectiveness (ε) is higher than the second threshold (ε2), deeming (160) the catalyst to be not faulty; when the effectiveness (ε) is between the first (ε1) and the second threshold (ε2), deeming the state of faultiness of the catalyst to be undetermined, and then intrusively determining (170) the ammonia storage capacity in order to eliminate the indeterminacy.